Rolling units are known, comprising rolling stands served by devices to adjust the gap between the rolls.
The device to adjust the gap allows to adjust their aperture and hence the section size of the rolled product to be obtained. Moreover, the adjustment device allows, for example after grinding operations, to re-use the rolling rolls whose diameter can vary as a function of the mechanical operations to which they have been subjected.
Each roll of a rolling stand is keyed to a shaft that is made to rotate in a known manner by drive members.
The pair of rolls in a rolling stand has the axes of rotation of the rolls disposed parallel to each other and orthogonal to the direction of rolling of the section shape.
The shafts supporting the rolls are supported by an eccentric bushing that is provided with a through hole in which each shaft of the rolls is housed.
The through hole of the eccentric bushing is made mis-aligned axially with respect to the longitudinal axis of the bushing. In this way, by making the eccentric bushing rotate, a variation is determined in the position of the axis of rotation of the shaft.
Each of the eccentric bushings is provided on the periphery with a toothing. The toothings of the eccentric bushings belonging to one pair of rolls engage in turn on a worm screw that is disposed in the inter-stand space of two adjacent rolling stands.
In particular, both the toothings of the eccentric bushings, when mounted, face with respect to a common side facing toward the stand upstream or the stand downstream of the rolling stand under consideration.
The worm screw is provided with a first threaded portion on which the toothing of one of the two rolls of the rolling stand engages, and with a second threaded portion that engages on the toothing of the other roll.
The first threaded portion and the second threaded portion respectively have a left-handed thread and a right-handed thread, or vice versa, so that when the worm screw is made to rotate, the toothings and hence the bushings are made to rotate in the same direction of rotation.
The eccentricity of the bushings entails that the axes of rotation of the rolls are reciprocally brought closer or distanced, and therefore entails an adjustment of the gap between the rolls.
The worm screw is disposed tangent with respect to both the toothed portions and between the rolling stand that is disposed upstream or respectively downstream with respect to the rolling stand under consideration.
The disposition of the worm screw in the intermediate space between two consecutive rolling stands entails an increase in the overall bulk of the rolling unit.
The bulk determines an increase in the distance between two adjacent rolling stands and it therefore becomes necessary to insert rolling guides for the rolled product being worked.
This entails an increase in the structural complexity of the rolling unit, and also an increase in the off-cuts of the head and tail ends of the product that is rolled.
Furthermore, even in the case where it is possible to reduce the overall bulk of the rolling unit in order to put the rolling stands adjacent to each other, the adjustment device is very expensive and complex to obtain.
In such cases, moreover, in order to further reduce the bulk between the rolling stands, the dimensional bulk of the inter-stand adjustment members is reduced, and the support structures thereof, that is, the worm screw. There is a consequent overall weakening of the bearing structure of the rolling unit and in particular of the bearing structure that supports the adjustment device.
Document DE 21 03 734 A1 describes a rolling stand with a system to adjust the gap between the rolls that consists of a worm screw that moves a pair of reciprocally engaging toothed wheels associated with the eccentric sleeve that supports a corresponding roll.
The position of the worm screw and the outermost toothed wheel determines an increase in the lateral bulk of the rolling stand, which does not allow to reduce the inter-stand space in the event of a close succession of stands in a rolling unit with two or more stands.
One purpose of the present invention is therefore to obtain a rolling unit that is extremely compact, simple and economical.
Another purpose of the present invention is to reduce the overall bulk of rolling machines, allowing a consequent reduction in the length of the works where the rolling plant is disposed.
Another purpose of the present invention is to obtain a rolling unit which does not require to use inter-stand guides to guide the section shape during rolling.
Another purpose of the present invention is to obtain a rolling unit that allows to further reduce rolling off-cuts of the head and tail ends of the products that are rolled.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.